With the intense competition between the two contenders for the Democratic presidential nomination, pundits have mused over whether Hillary Clinton’s appearance on "The Colbert Report" last night will give the former First Lady a so-called "Colbert bump," a surge in popularity which the show’s host claims will accrue to any politician that appears on the show.

Stephen Colbert first coined the eponymous term on his show after John Hall won in a close election to become a representative from New York in 2006 after an appearance on the "Report." Hall defeated incumbent Sue Kelly, who had declined to make an appearance on the show. Colbert himself commented on this after the election:

"And how did he beat Kelly? According to the American Prospect, quote, 'Her refusal to appear on cable's popular "The Colbert Report" may have also proved somewhat costly,'" Colbert reported, adding, "Somewhat? All what. She could've gotten the 'Colbert bump,' instead she got the 'Colbert dump.'"

Ever since, Colbert’s fans have been touting the powers of "the bump" in blogs, claiming it has boosted support for numerous politicians.

But most of the evidence cited lacks a certain amount of scientific rigor, said James Fowler, a political scientist at the University of California, San Diego, and a fan of the show.

"I saw people talking about the 'Colbert bump' online, but ... [they] took no account of the fact that most of the candidates who agreed to go on the show were running against candidates who really didn't have a chance of winning. They were very protected," Fowler said.

Stephen Colbert may be being "truthy" when he says an appearance on his show boosts politicians' popularity.

To really see if a "Colbert bump" exists, you have to compare the performance of political candidates who did appear on the show with those who didn't, Fowler says, and you have to do it by comparing apples to apples.

Incumbents must be matched to other incumbents, Democrats to other Democrats (the same goes for Republicans, of course). And because the study measured increased popularity by comparing campaign donations before and after an appearance, the amount of money candidates were taking in before their stint on the show had to match up.

Fowler jokes that the set-up is like running a medical study, where you have a control group and a treatment group. In this case, "Colbert is the treatment," Fowler said. His results will be published in an upcoming issue of PS: Political Science & Politics.

Democrat bump, Republican bust?
Fowler used Federal Election Commission data on all individual contributions made to U.S. House campaigns between Jan. 1, 2005, and Oct. 30, 2007, and used them to find matches for 47 candidates who appeared on "The Colbert Report" segment, "Better Know a District."

He compared both the number of donations and the amount of money received by each "Colbert candidate" to their match. The results showed that there might be, as Colbert himself would put it, some "truthiness" to the "Colbert bump" claims after all. At least for Democrats.

Democrats who appeared on the show raised about 44 percent more money after their appearance than they did before. Republicans, on the other hand, didn't fare as well after their Colbert appearance. Their appearance either had no effect, or a slightly negative one.

The first place many look is the show's audience, which has a perceived liberal leaning (though Fowler says there's no specific evidence of that). Fowler says this reason is plausible, but that the viewership of the "Report" is small, with a Nielsen average viewership of just 1.3 million for 2007. "I think it's incredibly unlikely that any of Colbert's viewers watch the show and then, you know, get out their checkbook," Fowler told LiveScience.

Fowler also rules out any agenda on the part of the show, since their main aim is to be funny. "They're just trying to get a laugh," he said. "Comedy first, news second."

More likely, Fowler says, is that the candidates are self-selecting their appearances on the show based on how they're doing beforehand.

"Republicans who agree to go on the show have to be doing much, much better than average in order to appear on the show," Fowler said his results showed. "So what this looks like is that Republicans have to be in an extremely confident position before they're willing to take a chance in being made fun of, whereas Democrats are just the opposite."

Democrats who agree to appear on the show are actually doing worse than the average candidate, "so Colbert seems more like an opportunity than a risk of destroying the campaign," Fowler added.

Ripple effect
Just how the show can have an effect with such a comparatively small audience, Fowler attributes to a ripple effect through the mainstream media. "When someone goes on his show, the fact that someone went on his show becomes news," Fowler said. "And a single appearance turns into an incident that's reported to 30 [million], 50 million people."

"His show is very influential among people who influence others," he added.

This could explain Mike Huckabee's upsurge in popularity after his "Colbert" appearance (which Colbert touted by saying he increased Huckabee's polling percentage by 300 percent – from 1 to 3 percent.) "The whole struggle in presidential primaries is just getting your name on people's minds," Fowler said, so Huckabee's appearance probably wouldn't have increased campaign donations (given the apparent Republican bust), but could've bumped him from a fifth to a second-place finish in a primary.

So what about Hillary? Whether or not Clinton's appearance on the show last night will boost her flagging popularity remains to be seen, but Fowler did notice that she made the announcement about her appearance the day after an editorial he wrote about his research appeared in The Los Angeles Times.